Conventionally, a post-processing apparatus connected with an image forming apparatus is provided with a binding section which binds a plurality of sheets printed paper into a bundle. As to the binding method in the binding section, a needle binding method and a gluing method are proposed.
The needle-binding type binding section arranged in the post-processing apparatus pierces a plurality of sheets of paper stacked on a processing tray with staples to bind the plurality of sheets of paper. When printed paper is stacked on the processing tray, the gluing-binding type binding section pastes glue to a given position of the paper and then places next printed paper on the paper.
In the needle-binding type binding section, the number of paper that can be bound at one time is limited according to the length of the used staple needle. Generally, as to the space above the processing tray, the rear side (opposite to the sheet discharge side) of the processing tray where the staple binding section is arranged is narrower than the front side (sheet discharge side) of the processing tray. Further, the paper binding section is generally arranged at the rear side of the processing tray. Thus, the maximum binding number of the binding section is limited.
Incidentally, when the number of paper that is fed from the image forming apparatus and is to be bound into one bundle is larger than the number of paper that can be bound into one bundle by the post-processing apparatus, neither the needle binding processing nor the glue binding processing can be carried out. Thus, it is desired that the paper can be bound into one bundle even if the printing number is larger than the number of paper that can be bound at one time.